Migrate 21a into ARP

[williamphelps13]

Description

Problem Statement

• When the 21a application was created it was unknown if there would be time in the 21a release timeline to have 21a in ARP. Having 21a in ARP means that 21a release is dependent on ARP Sign-In/Sign-Up, Header, and Footer being complete.
• As such 21a was created as its own application
• It has now been decided that there is time to complete these dependencies
• As such we need to migrate 21a into ARP

Implementation Details

• vets-website
  • src/applications/accreditation/21a --> src/applications/accredited-representative-portal/21a
  • Organize POA Requests content into its own sub-folder
  • Organize common elements that will serve both accreditation and POA Requests
  • Similar examples: src/applications/ivc-champva
• content-build
  • remove 21a from registry.json
• devops
  • update ansible/deployment/config/revproxy-vagov/vars/react_routes.yml
• vsp-platform-revproxy
  • update template-rendering/revproxy-vagov

Mockups/Designs

https://www.figma.com/design/2afIGOMII0uRI5ck1dWo1w/Form-21a---Apply-for-Accreditation-(CA-%26-Attorneys)?node-id=1026-23113&t=jRgivAFabaQuJxHs-4

• Note the ARP header and footer

Acceptance Criteria

• [ ] 21a has been migrated into ARP across all codebases
• [ ] There is a placeholder page for /accreditation
• [ ] ARP Login takes you to /accreditation instead of /poa-requests
• [ ] 21a has ARP header and footer

Automated Testing

• Update e2e tests based on the Acceptance Criteria's updating of the ARP portal

[williamphelps13]

Draft PR: #30835 87799 ARF migrate 21a into ARP (vets-website)

Next step in completing PR is around making Save in Progress work with the ARP frontend (which is technically a different Zenhub issue but it seems to need to be done in this PR because it is blocking the form from rendering)

[nihil2501]

@williamphelps13 tweak PR into yours of a basic error in the reducer structure we were returning. this should unlock the next more challenging phase of integrating SIP. see PR description.

[williamphelps13]

I picked up this issue because I had bandwidth for the 1-2pt issue that it was initially given but with the 4 form library fix issues I currently own (minItem validation and yes/no, address field, and date field fixes) and upcoming align steps with V3 design issues it seems best to pass this now 3-5pt issue to someone with more open bandwidth. Oren also created the initial POC that proposed using startReactApp instead of the standard startApp, but then he got pulled into Lighthouse before being able to implement it. The complexity of this issue is in this space.

After discussion with him and Gabe, Oren will take ownership of this issue and its PR (links are to the PRs themselves):

• vets-website
• content-build
• devops (change needed whenever create new route to make it accessible in staging/prod)
• vsp-platform-revproxy (where the above devops code is migrating to)

[gabezurita]

@nihil2501, @HaroldLee-VA, and @a6marinos, here's the issue that will likely be resolved by this work: https://app.zenhub.com/workspaces/accredited-representative-facing-team-65453a97a9cc36069a2ad1d6/issues/gh/department-of-veterans-affairs/va.gov-team/86193